Prior art mechanical couplings and fittings for joining pipe elements together end-to-end comprise interconnectable segments or housing portions that are positionable circumferentially surrounding the end portions of co-axially aligned pipe elements. The term “pipe element” is used herein to describe any pipe-like item or component having a pipe-like form. Pipe elements include pipe stock, pipe fittings such as elbows, caps and tees as well as fluid control components such as valves, reducers, strainers, restrictors, pressure regulators and the like.
Each mechanical coupling segment or housing portion has arcuate surfaces which project radially inwardly and engage plain end pipe elements, shoulder end pipe elements, shoulder and bead pipe elements or circumferential grooves that extend around each of the pipe elements to be joined. Engagement between the arcuate surfaces and the pipe elements provides mechanical restraint to the joint and ensures that the pipe elements remain coupled even under high internal pressure and external forces. The segments and housing portions define an annular channel that receives a sealing element, typically an elastomeric ring which engages the ends of each pipe element and cooperates with the segments or housing portions to provide a fluid tight seal. The segments and housing portions have connection members, typically in the form of lugs which project outwardly from the segments and housing portions. The lugs are adapted to receive fasteners, such as nuts and bolts, which are adjustably tightenable to draw the segments or housing portions toward one another.
To ensure a good fit between the couplings or fittings and the pipe elements, the arcuate surfaces according to the prior art have a radius of curvature that is substantially matched to the radius of curvature of the outer surface of the pipe element that it is intended to engage. For couplings or fittings used with grooved pipe elements, the radii of curvature of the arcuate surfaces are smaller than the radii of curvature of the outer surfaces of the pipe elements outside of the grooves so that the arcuate surfaces fit within and engage the grooves properly.
This geometrical relation between the arcuate surfaces of the couplings or fittings and the outer surfaces of the pipe elements according to the prior art results in a time consuming installation process when mechanical couplings or fittings are used. Typically, the coupling or fitting is received by the technician with the segments or housing portions bolted together and the sealing element captured within the segments or housing portions. The technician first disassembles the coupling or fitting by unbolting it, removes the sealing element, lubricates it (if not pre-lubricated) and places it around the ends of the pipe elements to be joined. Installation of the sealing element requires that it be lubricated and stretched significantly to accommodate the pipe elements, an often difficult and messy task, as the sealing element is usually stiff and the lubrication makes manual manipulation of the seal difficult. With the sealing element in place on both pipe elements, the segments or housing portions are then placed one at a time straddling the ends of the pipe elements and capturing the sealing element against them. During placement, the segments or housing portions engage the sealing element, the arcuate surfaces are aligned with the grooves when present, or with alignment marks made on the outside surfaces of the pipe elements, the bolts are inserted through the lugs, the nuts are threaded onto the bolts and tightened, drawing the coupling segments or housing portions toward one another, compressing the sealing element and engaging the arcuate surface within the grooves.
As evident from the previous description, installation of mechanical pipe couplings and fittings according to the prior art requires that the technician typically handle at least seven individual piece parts (and more when the coupling has more than two segments), and must totally disassemble and reassemble the coupling or fitting. Significant time, effort and expense would be saved if the technician could install a mechanical pipe coupling or fitting without first totally disassembling it and then reassembling it, piece by piece.